Swift Optimizer: add the fixStackNesting utility in PassContext

This bridges to the StackNesting utility in C++

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/PassManager/PassUtils.swift

@@ -111,6 +111,10 @@ struct PassContext {
 
     RefCountingInst_setIsAtomic(instruction.bridged, isAtomic)
   }
+  
+  func fixStackNesting(function: Function) {
+    PassContext_fixStackNesting(_bridged, function.bridged)
+  }
 }
 
 struct FunctionPass {

include/swift/SILOptimizer/OptimizerBridging.h

@@ -119,6 +119,9 @@ BridgedSlab PassContext_allocSlab(BridgedPassContext passContext,
 BridgedSlab PassContext_freeSlab(BridgedPassContext passContext,
                                  BridgedSlab slab);
 
+void PassContext_fixStackNesting(BridgedPassContext context,
+                                 BridgedFunction function);
+
 BridgedBasicBlockSet PassContext_allocBasicBlockSet(BridgedPassContext context);
 void PassContext_freeBasicBlockSet(BridgedPassContext context,
                                    BridgedBasicBlockSet set);

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -28,6 +28,7 @@
 #include "swift/SILOptimizer/PassManager/PrettyStackTrace.h"
 #include "swift/SILOptimizer/PassManager/Transforms.h"
 #include "swift/SILOptimizer/Utils/OptimizerStatsUtils.h"
+#include "swift/SILOptimizer/Utils/StackNesting.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -1225,6 +1226,20 @@ void PassContext_eraseInstruction(BridgedPassContext passContext,
   castToPassInvocation(passContext)->eraseInstruction(castToInst(inst));
 }
 
+void PassContext_fixStackNesting(BridgedPassContext passContext,
+                                 BridgedFunction function) {
+  switch (StackNesting::fixNesting(castToFunction(function))) {
+    case StackNesting::Changes::None:
+      break;
+    case StackNesting::Changes::Instructions:
+      PassContext_notifyChanges(passContext, instructionsChanged);
+      break;
+    case StackNesting::Changes::CFG:
+      PassContext_notifyChanges(passContext, branchesChanged);
+      break;
+  }
+}
+
 SwiftInt PassContext_isSwift51RuntimeAvailable(BridgedPassContext context) {
   SILPassManager *pm = castToPassInvocation(context)->getPassManager();
   ASTContext &ctxt = pm->getModule()->getASTContext();